1. Field of the Invention
The present invention relates generally to broadcast systems, and more particularly, to a method and apparatus for transmitting and receiving a data stream in digital video broadcast systems.
2. Description of the Related Art
A broadcast system, such as a Digital Video Broadcasting (DVB) system, may transmit data in the form of a sequence of frames. A DVB system may operate according to, for example, a DVB Terrestrial 2nd Generation (DVB-T2) standard, Advanced Televisions Systems Committee (ATSC), Integrated Services Digital Broadcasting (ISDB), or Digital Multimedia Broadcasting (DMB). Each frame typically includes a preamble section and a data section. The preamble section and the data section are time-multiplexed. The data section may carry data arranged in the form of a number of data streams, which may be referred to as Physical Layer Pipes (PLP). A PLP or a plurality of PLPs may carry, for example, a service such as a video channel that is to be provided to a user. Reception of data from the frames, and reception of the data streams, may be assisted by signalling, which may typically be carried in the preamble of the frame, in which case the signalling is referred to as Out-of-Band (OB) signalling. The signalling may also be carried in the data section, in which case the signalling is referred to as In-Band (IB) signalling. The signalling may be referred to as physical layer signalling, or Layer 1 (L1) signalling. The signalling may indicate a modulation or coding scheme to be used for decoding data, and it may, for example, indicate sections of a data field to be decoded, or the location of a data stream within the data section.
The use of signal compression techniques has increased, and lower data rate services, which may be more robust in particular in mobile environments, have been provided. Accordingly, the number of data streams carried by a sequence of frames is potentially large, but thinly spread in the sense that not every frame may carry all of the data streams. Because signalling is typically required relating to each data stream for each frame, the signalling may represent a large overhead per frame in terms of data capacity and receiver power consumption.
Furthermore, since data streams are typically frequency interleaved within symbols transmitted in a data frame, it is necessary for a receiver to receive the whole symbol bandwidth in order to receive a data stream. As a result, the sampling rate used at the receiver is typically required to be sufficient to receive the whole symbol bandwidth, which places demands on the power consumption of the receiver. The power consumption of the receiver is related to the sampling rate. Power consumption is a particularly important parameter, in particular for battery-powered digital broadcasting receivers. Data streams may also be time interleaved within data blocks, and mapping of the data blocks to data frames for transmission may be inefficient.